Fluid dynamics calculations to estimate the stenosis related fractional flow reserve (FFR) based on single phase CT coronary angiography data sets are currently being evaluated in clinical studies. These calculations intend to deliver an additional functional parameter next to the spatial measurement of the degree of stenosis. The method is based on the segmentation of the coronary artery tree from a cardiac CT data set of a patient and subsequent simulation of blood flow velocity and pressure distribution in the vascular subsystem containing the stenosis.
The calculated quantity which is assumed to be clinically relevant is the fractional flow reserve, namely the pressure drop across a stenosis. The fluid dynamics calculations rely on different input data. In the first instance it is the geometry of the coronary arteries which determines the result of the flow simulation. However, other personalized boundary conditions like the blood flow velocity at the vessel inlet and/or the blood pressure may be important. The spatial dynamics of the coronary arteries due to the cardiac motion is currently neglected.
US 2012/0072190 A1 discloses a method and system for non-invasive patient-specific assessment of coronary artery disease. An anatomical model of a coronary artery is generated from medical image data. A velocity of blood in the coronary artery is estimated based on a spatio-temporal representation of contrast agent propagation in the medical image data. Blood flow is simulated in the anatomical model of the coronary artery using a computational fluid dynamics (CFD) simulation using the estimated velocity of the blood in the coronary artery as a boundary condition.
Further, Kim et al., Patient-Specific Modeling of Blood Flow and Pressure in Human Coronary Arteries, Annals of Biomedical Engineering, Vol. 38, No. 10, October 2010, pp. 3195-3209 discloses a method that predicts coronary flow and pressure of three-dimensional epicardial coronary arteries by considering models of the heart and arterial system and the interactions between the two models. For each coronary outlet, a lumped parameter coronary vascular bed model was assigned to represent the impedance of the downstream coronary vascular networks absent in the computational domain. The intramyocardial pressure was represented with either the left or right ventricular pressure depending on the location of the coronary arteries. The left and right ventricular pressure were solved from the lumped parameter heart models coupled to a closed loop system comprising a three-dimensional model of the aorta, three-element Windkessel models of the rest of the systemic circulation and the pulmonary circulation, and lumped parameter models for the left and right sides of the heart.